Columnar Organization of Head-to-Tail Self-Assembled Pt4 Rings

Coordination of Pt2+ to a family of tunable Schiff base proligands directs the 12-component self-assembly of disk-shaped Pt-4 rings in a head-to-tail fashion. Aggregation of these S-4 symmetric Pt-4 macrocycles into columnar architectures was investigated by dynamic and static light scattering, NMR spectroscopy, powder X-ray diffraction, and transmission electron microscopy. Data from these experiments support the formation of columnar architectures for all of the structures studied except when bulky tris(4-tert-butylphenyl)methyl substituents were present. In this case, aggregation was limited to dimers in CHCl3 (K-dim = 3200 +/- 200 L mol(-1) at 25 degrees C) and a thermodynamic analysis revealed that dimerization is an entropy driven process. Columnar architectures of Pt-4 rings with branched 2-hexyldecyl substituents organize into lyotropic mesophases in nonpolar organic solvents. These new self-assembled supramolecules are promising candidates to access nanotubes with multiple linear arrays of Pt2+ ions.